Conventional peel-type blind rivets comprise an outer tubular shell having an enlarged flange at one end, having a mandrel associated therewith with a stem extending through the tubular rivet so as to be coaxial therewith. The stem has a radially enlarged head at one end for engagement with an end face of the rivet, opposed to the enlarged flange. The periphery of the radially enlarged head of the mandrel is equal to or slightly smaller than the external circumference of the rivet shell, so that both parts can be inserted together through the aperture in the workpiece from a front side thereof until the flange of the rivet engages with the front surface of the workpiece. The enlarged head of the mandrel of peel-type blind rivets will comprise a plurality of cutting edges radially inclined between the outer circumference of the mandrel head and the stem so that in operation, as a tensile force is applied to the stem to draw the head into the rivet body, these edges are displaced against the rivet body thereby cutting or splitting the body into a plurality of segments whereby continued displacement of the enlarged head into the split rivet body causes “peel” like displacement of the segments until they engage with a rear side of the workpieces to hold the rivet body in the aperture and to compress the workpieces between these split segments and the flange of the rivet body. A continued application of the tensile force during the setting process then causes the mandrel stem to break, usually at a neck portion specifically designed to fail at a predetermined load, so as to remove the mandrel. This stem break results in a release of strain energy which causes the mandrel head part, which is temporarily lodged in the split end of the peeled back rivet shell, to be dislodged from its position and to move in the opposite direction to that in which it was previously pulled so that the mandrel head and the remaining part of the mandrel stem are both ejected from the rivet shell during the setting process.
Peel-type blind rivets of this type are well known and have been sold by the assignee of the present application under the registered Trade Mark POP® for several years.
However, there are instances whereby the ejection of the mandrel head from the peel-type blind rivet is undesirable, specifically where the rivet is being installed in the proximity of moving parts, or where electrical equipment is being installed and the dislodged mandrel head could effect contact with live electrical terminals. Of course, it is also desirable not to have a loose piece of metal “rattling” around in any sealed container utilising such peel-type blind rivets.
It is an object of the present invention to provide an improved type of peel-type blind rivet which alleviates the aforementioned problems and restrains the mandrel head in the rivet body after setting.